Rollerblading is a terrific way to build some solid and well shaped thighs...
...but if you REALLY want them to grow fast, either run or cycle up hills or stairs. Uphill training is the best way to obtain fast results for thighs. As an added perk your butt will follow suit and be chisseled nicely as well.
exercise, I'd say aerobic, but its gona take some time,...the best time to do it would be in the morning right after you wake up; as your glycogen stores would be fairly low. Good luck, if it helps any you should try drinking green tea, and do some outdoor activities.
my legs look like that and I was a gymnast for 9 years a dancer for 6 and a cheerleader for 12 years and counting, so join of of those three or all, and if you don't like any of those try soccer I was also in that for 3 years. any sport would really help but those are the ones I'm in/ was in and thet have gave me an amazing body.